Sample Preparation Influences pXRF Results: A Case Study on a Tailings Pond

The concentrations of PTEs and Fe₂O₃ increase from the sand fraction to the silt fraction, although the magnitude of this increase is not uniform (Zn > Cu > As > Pb), while SiO₂ content is not affected by particle size. In general, PTE concentrations are lower in wet samples than in dry samples. The ratio of the element concentration in the wet sample to that in the air-dried sample, together with the gravimetric moisture content (%), were plotted in central scatter plots, which allowed the identification of outliers. The inverse relationship observed between the concentration of certain elements and moisture content may be explained by the geochemical characteristics of the sample. Moisture in both manually and mechanically ground samples influences analytical ac-curacy, even when the processing time is identical. Triplicate samples indicate small-scale heterogeneity driven by post-depositional alteration of the tailings, as well as element associations (e.g., Fe₂O₃–As) dictated by the mineralogical composition of the source material (e.g., arsenopyrite).